1. Field of the Invention
The present invention relates to a solid-state electronic image pickup apparatus comprising an image sensor having a lot of photoelectric conversion devices (transducers) (pixels) arranged two dimensionally and capable of being selective readout (random access) and a method of driving the same, and an electronic camera including the solid-state electronic image pickup apparatus.
2. Description of the Background Art
In image sensors capable of being selective readout (such as a CMOS (Complementary Metal-Oxide Semiconductor) type and a CID (Charge Injection Device) type) as shown in FIG. 13, signal charges respectively accumulated in photoelectric conversion devices are successively outputted for each pixel (photoelectric conversion device) as a video signal corresponding to one frame. The video signal outputted from the image sensor is inputted to an analog processing circuit including an amplification circuit, a correlated double sampling circuit, and an analog-to-digital conversion circuit. A video signal corresponding to the subsequent pixel cannot be inputted to the analog processing circuit until analog processing (in FIG. 13, only the term “PRO.” is shown) for one pixel (one photoelectric conversion device) is terminated in the analog processing circuit. The time period required for analog processing of the video signal (signal charge) for one pixel in the analog processing circuit is referred to as a pixel rate (the unit thereof is a frequency or time period which is a reciprocal of the frequency). Then, the time period required for analog processing of the video signal for one frame (referred to as a frame rate: the unit thereof is a frequency or time period) is more than the time period corresponding to the product of the pixel rate and the number of pixels (photoelectric conversion devices) provided on the image sensor.
In the above type of image sensor, the signal charge accumulation time period (exposure time period) of the photoelectric conversion device may be arbitrary set, so that even if there is a limit to shorten the pixel rate, this limit does not affect the shutter speed.
However, in a case of strobe flash (electronic flash) imaging, all the photoelectric conversion devices on the image sensor have to be exposed simultaneously in the time period of strobe flash (flash synchronization). As a result, the shutter speed becomes low and frame rate becomes long.